This invention relates to the preparation of metallopolysilanes. More specifically, this invention relates to the preparation of metallopolysilanes which contain significant amounts of aluminum, boron, chromium, molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, niobium, or tantalum. These polymers are useful as chemical intermediates to synthesize other metal-containing organosilicon materials or polymers. These polymers can also be converted, when fired at high temperatures, to ceramic materials.
What is disclosed herein is a novel process to obtain metallopolysilanes by reacting polysilanes with certain metal-containing compounds or complexes. The metals are oxidatively added to the polysilane. Polysilanes with significantly higher metallic levels, relative to other methods of incorporating the metal components, can be prepared by the processes of this invention.
Chandra et al. in U.S. Pat. No. 4,762,895 described a method of preparing metallopolysilanes by reacting organohalogendisilanes with metal-containing compounds (such as metal halides) in the presence of a redistribution catalyst in an inert, essentially anhydrous atmosphere and removing volatile byproducts. The metal components were incorporated into the polysilane during the actual formation of the polysilane. The highest level of metal incorporation reported was about five weight percent; generally, the reported metal content of the metal-containing polysilanes was less than about two weight percent.
In Japanese Kokai Tokyo Koho Nos. 58/213023 and 59/161430 titanium- or zirconium-containing preceramic polymers were prepared by reacting polysilanes with titanium alkoxides or zirconium alkoxides. Such materials are expected to contain [Ti-O] and [Zr-O] units.
What is newly discovered is that metallopolysilanes can be prepared by reacting polysilanes with certain metallic compounds under conditions where open or unoccupied coordination sites can be generated.